The present invention relates to a transport apparatus in which a runner is driven or stopped by a forward or reverse impelling force applied externally.
Among the conventional apparatuses of this type is a transport apparatus using a linear induction motor. In this apparatus, a reaction plate is attached to the runner, and stators as impelling force exerting means are arranged at predetermined intervals along a transport path of the runner. The stators are energized by a power supply unit so that magnetic flux, which changes with time, is applied to the reaction plate. The change of the magnetic flux produces a forward or reverse fixed impelling force to the reaction plate, thereby driving or stopping the runner.
If the power supply for the stators is out of order due to power failure or an operator's mistake, the runner will possibly stop at a position halfway between two adjacent stators. In such a position, the runner will not be able to be started by an impelling force.
Conventionally, therefore, the runner is returned to any of predetermined positions corresponding to the stators by the following methods.
(1) When the power supply is restored, the stopped runner is removed from the transport path by means of another runner which is subjected to the impelling force from the stators.
(2) The middle portion of the transport path is located higher than the predetermined positions corresponding to the stators so that the runner is moved to and stopped at one such predetermined position by gravity.
(3) The runner is moved manually.
In methods (1) and (3), it takes much time and labor to return the stopped runner to a position from which it can start. On the other hand, method (2) prohibits a free layout of the transport path.